// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2012 Gael Guennebaud <gael.guennebaud@inria.fr>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

#ifndef EIGEN_REF_H
#define EIGEN_REF_H

namespace Eigen {

namespace internal {

    template <typename _PlainObjectType, int _Options, typename _StrideType>
    struct traits<Ref<_PlainObjectType, _Options, _StrideType>> : public traits<Map<_PlainObjectType, _Options, _StrideType>>
    {
        typedef _PlainObjectType PlainObjectType;
        typedef _StrideType StrideType;
        enum
        {
            Options = _Options,
            Flags = traits<Map<_PlainObjectType, _Options, _StrideType>>::Flags | NestByRefBit,
            Alignment = traits<Map<_PlainObjectType, _Options, _StrideType>>::Alignment
        };

        template <typename Derived> struct match
        {
            enum
            {
                IsVectorAtCompileTime = PlainObjectType::IsVectorAtCompileTime || Derived::IsVectorAtCompileTime,
                HasDirectAccess = internal::has_direct_access<Derived>::ret,
                StorageOrderMatch = IsVectorAtCompileTime || ((PlainObjectType::Flags & RowMajorBit) == (Derived::Flags & RowMajorBit)),
                InnerStrideMatch = int(StrideType::InnerStrideAtCompileTime) == int(Dynamic) ||
                                   int(StrideType::InnerStrideAtCompileTime) == int(Derived::InnerStrideAtCompileTime) ||
                                   (int(StrideType::InnerStrideAtCompileTime) == 0 && int(Derived::InnerStrideAtCompileTime) == 1),
                OuterStrideMatch = IsVectorAtCompileTime || int(StrideType::OuterStrideAtCompileTime) == int(Dynamic) ||
                                   int(StrideType::OuterStrideAtCompileTime) == int(Derived::OuterStrideAtCompileTime),
                // NOTE, this indirection of evaluator<Derived>::Alignment is needed
                // to workaround a very strange bug in MSVC related to the instantiation
                // of has_*ary_operator in evaluator<CwiseNullaryOp>.
                // This line is surprisingly very sensitive. For instance, simply adding parenthesis
                // as "DerivedAlignment = (int(evaluator<Derived>::Alignment))," will make MSVC fail...
                DerivedAlignment = int(evaluator<Derived>::Alignment),
                AlignmentMatch =
                    (int(traits<PlainObjectType>::Alignment) == int(Unaligned)) ||
                    (DerivedAlignment >= int(Alignment)),  // FIXME the first condition is not very clear, it should be replaced by the required alignment
                ScalarTypeMatch = internal::is_same<typename PlainObjectType::Scalar, typename Derived::Scalar>::value,
                MatchAtCompileTime = HasDirectAccess && StorageOrderMatch && InnerStrideMatch && OuterStrideMatch && AlignmentMatch && ScalarTypeMatch
            };
            typedef typename internal::conditional<MatchAtCompileTime, internal::true_type, internal::false_type>::type type;
        };
    };

    template <typename Derived> struct traits<RefBase<Derived>> : public traits<Derived>
    {
    };

}  // namespace internal

template <typename Derived> class RefBase : public MapBase<Derived>
{
    typedef typename internal::traits<Derived>::PlainObjectType PlainObjectType;
    typedef typename internal::traits<Derived>::StrideType StrideType;

public:
    typedef MapBase<Derived> Base;
    EIGEN_DENSE_PUBLIC_INTERFACE(RefBase)

    EIGEN_DEVICE_FUNC EIGEN_CONSTEXPR inline Index innerStride() const { return StrideType::InnerStrideAtCompileTime != 0 ? m_stride.inner() : 1; }

    EIGEN_DEVICE_FUNC EIGEN_CONSTEXPR inline Index outerStride() const
    {
        return StrideType::OuterStrideAtCompileTime != 0 ? m_stride.outer() :
                                                           IsVectorAtCompileTime ? this->size() : int(Flags) & RowMajorBit ? this->cols() : this->rows();
    }

    EIGEN_DEVICE_FUNC RefBase()
        : Base(0, RowsAtCompileTime == Dynamic ? 0 : RowsAtCompileTime, ColsAtCompileTime == Dynamic ? 0 : ColsAtCompileTime),
          // Stride<> does not allow default ctor for Dynamic strides, so let' initialize it with dummy values:
          m_stride(StrideType::OuterStrideAtCompileTime == Dynamic ? 0 : StrideType::OuterStrideAtCompileTime,
                   StrideType::InnerStrideAtCompileTime == Dynamic ? 0 : StrideType::InnerStrideAtCompileTime)
    {
    }

    EIGEN_INHERIT_ASSIGNMENT_OPERATORS(RefBase)

protected:
    typedef Stride<StrideType::OuterStrideAtCompileTime, StrideType::InnerStrideAtCompileTime> StrideBase;

    // Resolves inner stride if default 0.
    static EIGEN_DEVICE_FUNC EIGEN_CONSTEXPR Index resolveInnerStride(Index inner) { return inner == 0 ? 1 : inner; }

    // Resolves outer stride if default 0.
    static EIGEN_DEVICE_FUNC EIGEN_CONSTEXPR Index
    resolveOuterStride(Index inner, Index outer, Index rows, Index cols, bool isVectorAtCompileTime, bool isRowMajor)
    {
        return outer == 0 ? isVectorAtCompileTime ? inner * rows * cols : isRowMajor ? inner * cols : inner * rows : outer;
    }

    // Returns true if construction is valid, false if there is a stride mismatch,
    // and fails if there is a size mismatch.
    template <typename Expression> EIGEN_DEVICE_FUNC bool construct(Expression& expr)
    {
        // Check matrix sizes.  If this is a compile-time vector, we do allow
        // implicitly transposing.
        EIGEN_STATIC_ASSERT(EIGEN_PREDICATE_SAME_MATRIX_SIZE(PlainObjectType, Expression)
                                // If it is a vector, the transpose sizes might match.
                                || (PlainObjectType::IsVectorAtCompileTime &&
                                    ((int(PlainObjectType::RowsAtCompileTime) == Eigen::Dynamic || int(Expression::ColsAtCompileTime) == Eigen::Dynamic ||
                                      int(PlainObjectType::RowsAtCompileTime) == int(Expression::ColsAtCompileTime)) &&
                                     (int(PlainObjectType::ColsAtCompileTime) == Eigen::Dynamic || int(Expression::RowsAtCompileTime) == Eigen::Dynamic ||
                                      int(PlainObjectType::ColsAtCompileTime) == int(Expression::RowsAtCompileTime)))),
                            YOU_MIXED_MATRICES_OF_DIFFERENT_SIZES)

        // Determine runtime rows and columns.
        Index rows = expr.rows();
        Index cols = expr.cols();
        if (PlainObjectType::RowsAtCompileTime == 1)
        {
            eigen_assert(expr.rows() == 1 || expr.cols() == 1);
            rows = 1;
            cols = expr.size();
        }
        else if (PlainObjectType::ColsAtCompileTime == 1)
        {
            eigen_assert(expr.rows() == 1 || expr.cols() == 1);
            rows = expr.size();
            cols = 1;
        }
        // Verify that the sizes are valid.
        eigen_assert((PlainObjectType::RowsAtCompileTime == Dynamic) || (PlainObjectType::RowsAtCompileTime == rows));
        eigen_assert((PlainObjectType::ColsAtCompileTime == Dynamic) || (PlainObjectType::ColsAtCompileTime == cols));

        // If this is a vector, we might be transposing, which means that stride should swap.
        const bool transpose = PlainObjectType::IsVectorAtCompileTime && (rows != expr.rows());
        // If the storage format differs, we also need to swap the stride.
        const bool row_major = ((PlainObjectType::Flags)&RowMajorBit) != 0;
        const bool expr_row_major = (Expression::Flags & RowMajorBit) != 0;
        const bool storage_differs = (row_major != expr_row_major);

        const bool swap_stride = (transpose != storage_differs);

        // Determine expr's actual strides, resolving any defaults if zero.
        const Index expr_inner_actual = resolveInnerStride(expr.innerStride());
        const Index expr_outer_actual =
            resolveOuterStride(expr_inner_actual, expr.outerStride(), expr.rows(), expr.cols(), Expression::IsVectorAtCompileTime != 0, expr_row_major);

        // If this is a column-major row vector or row-major column vector, the inner-stride
        // is arbitrary, so set it to either the compile-time inner stride or 1.
        const bool row_vector = (rows == 1);
        const bool col_vector = (cols == 1);
        const Index inner_stride = ((!row_major && row_vector) || (row_major && col_vector)) ?
                                       (StrideType::InnerStrideAtCompileTime > 0 ? Index(StrideType::InnerStrideAtCompileTime) : 1) :
                                       swap_stride ? expr_outer_actual : expr_inner_actual;

        // If this is a column-major column vector or row-major row vector, the outer-stride
        // is arbitrary, so set it to either the compile-time outer stride or vector size.
        const Index outer_stride = ((!row_major && col_vector) || (row_major && row_vector)) ?
                                       (StrideType::OuterStrideAtCompileTime > 0 ? Index(StrideType::OuterStrideAtCompileTime) : rows * cols * inner_stride) :
                                       swap_stride ? expr_inner_actual : expr_outer_actual;

        // Check if given inner/outer strides are compatible with compile-time strides.
        const bool inner_valid =
            (StrideType::InnerStrideAtCompileTime == Dynamic) || (resolveInnerStride(Index(StrideType::InnerStrideAtCompileTime)) == inner_stride);
        if (!inner_valid)
        {
            return false;
        }

        const bool outer_valid =
            (StrideType::OuterStrideAtCompileTime == Dynamic) ||
            (resolveOuterStride(
                 inner_stride, Index(StrideType::OuterStrideAtCompileTime), rows, cols, PlainObjectType::IsVectorAtCompileTime != 0, row_major) ==
             outer_stride);
        if (!outer_valid)
        {
            return false;
        }

        ::new (static_cast<Base*>(this)) Base(expr.data(), rows, cols);
        ::new (&m_stride)
            StrideBase((StrideType::OuterStrideAtCompileTime == 0) ? 0 : outer_stride, (StrideType::InnerStrideAtCompileTime == 0) ? 0 : inner_stride);
        return true;
    }

    StrideBase m_stride;
};

/** \class Ref
  * \ingroup Core_Module
  *
  * \brief A matrix or vector expression mapping an existing expression
  *
  * \tparam PlainObjectType the equivalent matrix type of the mapped data
  * \tparam Options specifies the pointer alignment in bytes. It can be: \c #Aligned128, , \c #Aligned64, \c #Aligned32, \c #Aligned16, \c #Aligned8 or \c #Unaligned.
  *                 The default is \c #Unaligned.
  * \tparam StrideType optionally specifies strides. By default, Ref implies a contiguous storage along the inner dimension (inner stride==1),
  *                   but accepts a variable outer stride (leading dimension).
  *                   This can be overridden by specifying strides.
  *                   The type passed here must be a specialization of the Stride template, see examples below.
  *
  * This class provides a way to write non-template functions taking Eigen objects as parameters while limiting the number of copies.
  * A Ref<> object can represent either a const expression or a l-value:
  * \code
  * // in-out argument:
  * void foo1(Ref<VectorXf> x);
  *
  * // read-only const argument:
  * void foo2(const Ref<const VectorXf>& x);
  * \endcode
  *
  * In the in-out case, the input argument must satisfy the constraints of the actual Ref<> type, otherwise a compilation issue will be triggered.
  * By default, a Ref<VectorXf> can reference any dense vector expression of float having a contiguous memory layout.
  * Likewise, a Ref<MatrixXf> can reference any column-major dense matrix expression of float whose column's elements are contiguously stored with
  * the possibility to have a constant space in-between each column, i.e. the inner stride must be equal to 1, but the outer stride (or leading dimension)
  * can be greater than the number of rows.
  *
  * In the const case, if the input expression does not match the above requirement, then it is evaluated into a temporary before being passed to the function.
  * Here are some examples:
  * \code
  * MatrixXf A;
  * VectorXf a;
  * foo1(a.head());             // OK
  * foo1(A.col());              // OK
  * foo1(A.row());              // Compilation error because here innerstride!=1
  * foo2(A.row());              // Compilation error because A.row() is a 1xN object while foo2 is expecting a Nx1 object
  * foo2(A.row().transpose());  // The row is copied into a contiguous temporary
  * foo2(2*a);                  // The expression is evaluated into a temporary
  * foo2(A.col().segment(2,4)); // No temporary
  * \endcode
  *
  * The range of inputs that can be referenced without temporary can be enlarged using the last two template parameters.
  * Here is an example accepting an innerstride!=1:
  * \code
  * // in-out argument:
  * void foo3(Ref<VectorXf,0,InnerStride<> > x);
  * foo3(A.row());              // OK
  * \endcode
  * The downside here is that the function foo3 might be significantly slower than foo1 because it won't be able to exploit vectorization, and will involve more
  * expensive address computations even if the input is contiguously stored in memory. To overcome this issue, one might propose to overload internally calling a
  * template function, e.g.:
  * \code
  * // in the .h:
  * void foo(const Ref<MatrixXf>& A);
  * void foo(const Ref<MatrixXf,0,Stride<> >& A);
  *
  * // in the .cpp:
  * template<typename TypeOfA> void foo_impl(const TypeOfA& A) {
  *     ... // crazy code goes here
  * }
  * void foo(const Ref<MatrixXf>& A) { foo_impl(A); }
  * void foo(const Ref<MatrixXf,0,Stride<> >& A) { foo_impl(A); }
  * \endcode
  *
  * See also the following stackoverflow questions for further references:
  *  - <a href="http://stackoverflow.com/questions/21132538/correct-usage-of-the-eigenref-class">Correct usage of the Eigen::Ref<> class</a>
  *
  * \sa PlainObjectBase::Map(), \ref TopicStorageOrders
  */
template <typename PlainObjectType, int Options, typename StrideType> class Ref : public RefBase<Ref<PlainObjectType, Options, StrideType>>
{
private:
    typedef internal::traits<Ref> Traits;
    template <typename Derived>
    EIGEN_DEVICE_FUNC inline Ref(const PlainObjectBase<Derived>& expr,
                                 typename internal::enable_if<bool(Traits::template match<Derived>::MatchAtCompileTime), Derived>::type* = 0);

public:
    typedef RefBase<Ref> Base;
    EIGEN_DENSE_PUBLIC_INTERFACE(Ref)

#ifndef EIGEN_PARSED_BY_DOXYGEN
    template <typename Derived>
    EIGEN_DEVICE_FUNC inline Ref(PlainObjectBase<Derived>& expr,
                                 typename internal::enable_if<bool(Traits::template match<Derived>::MatchAtCompileTime), Derived>::type* = 0)
    {
        EIGEN_STATIC_ASSERT(bool(Traits::template match<Derived>::MatchAtCompileTime), STORAGE_LAYOUT_DOES_NOT_MATCH);
        // Construction must pass since we will not create temprary storage in the non-const case.
        const bool success = Base::construct(expr.derived());
        EIGEN_UNUSED_VARIABLE(success)
        eigen_assert(success);
    }
    template <typename Derived>
    EIGEN_DEVICE_FUNC inline Ref(const DenseBase<Derived>& expr,
                                 typename internal::enable_if<bool(Traits::template match<Derived>::MatchAtCompileTime), Derived>::type* = 0)
#else
    /** Implicit constructor from any dense expression */
    template <typename Derived> inline Ref(DenseBase<Derived>& expr)
#endif
    {
        EIGEN_STATIC_ASSERT(bool(internal::is_lvalue<Derived>::value), THIS_EXPRESSION_IS_NOT_A_LVALUE__IT_IS_READ_ONLY);
        EIGEN_STATIC_ASSERT(bool(Traits::template match<Derived>::MatchAtCompileTime), STORAGE_LAYOUT_DOES_NOT_MATCH);
        EIGEN_STATIC_ASSERT(!Derived::IsPlainObjectBase, THIS_EXPRESSION_IS_NOT_A_LVALUE__IT_IS_READ_ONLY);
        // Construction must pass since we will not create temporary storage in the non-const case.
        const bool success = Base::construct(expr.const_cast_derived());
        EIGEN_UNUSED_VARIABLE(success)
        eigen_assert(success);
    }

    EIGEN_INHERIT_ASSIGNMENT_OPERATORS(Ref)
};

// this is the const ref version
template <typename TPlainObjectType, int Options, typename StrideType>
class Ref<const TPlainObjectType, Options, StrideType> : public RefBase<Ref<const TPlainObjectType, Options, StrideType>>
{
    typedef internal::traits<Ref> Traits;

public:
    typedef RefBase<Ref> Base;
    EIGEN_DENSE_PUBLIC_INTERFACE(Ref)

    template <typename Derived>
    EIGEN_DEVICE_FUNC inline Ref(const DenseBase<Derived>& expr,
                                 typename internal::enable_if<bool(Traits::template match<Derived>::ScalarTypeMatch), Derived>::type* = 0)
    {
        //      std::cout << match_helper<Derived>::HasDirectAccess << "," << match_helper<Derived>::OuterStrideMatch << "," << match_helper<Derived>::InnerStrideMatch << "\n";
        //      std::cout << int(StrideType::OuterStrideAtCompileTime) << " - " << int(Derived::OuterStrideAtCompileTime) << "\n";
        //      std::cout << int(StrideType::InnerStrideAtCompileTime) << " - " << int(Derived::InnerStrideAtCompileTime) << "\n";
        construct(expr.derived(), typename Traits::template match<Derived>::type());
    }

    EIGEN_DEVICE_FUNC inline Ref(const Ref& other) : Base(other)
    {
        // copy constructor shall not copy the m_object, to avoid unnecessary malloc and copy
    }

    template <typename OtherRef> EIGEN_DEVICE_FUNC inline Ref(const RefBase<OtherRef>& other)
    {
        construct(other.derived(), typename Traits::template match<OtherRef>::type());
    }

protected:
    template <typename Expression> EIGEN_DEVICE_FUNC void construct(const Expression& expr, internal::true_type)
    {
        // Check if we can use the underlying expr's storage directly, otherwise call the copy version.
        if (!Base::construct(expr))
        {
            construct(expr, internal::false_type());
        }
    }

    template <typename Expression> EIGEN_DEVICE_FUNC void construct(const Expression& expr, internal::false_type)
    {
        internal::call_assignment_no_alias(m_object, expr, internal::assign_op<Scalar, Scalar>());
        Base::construct(m_object);
    }

protected:
    TPlainObjectType m_object;
};

}  // end namespace Eigen

#endif  // EIGEN_REF_H
